Manufacture of direct ammonium sulphate



Aug. 15, 1933. W, B. WINGERT MANUFACTURE OF DIRECT AMMONIUM SULPHATE Filed Jan. 24, 1929 l '4?5 produceddirectly and may be recovered. The

gases pass then through an acid separator into a Patented Aug. 15, 1933 N UNITED STATES PATENT OFFICE f f MANUFACTURE oF DIRECT AMMONIUM v sULPHATE 2 Claims. (Cl. .Z3- 196) ThisV invention relates tocoal distillation and `more particularly tothe recovery of ammonium sulphate from gasesderived from the distillation of coal.

conveyed to the saturators and there Xed as ammonium sulphate. The operationas described entails numerous diiliculties and involves considerable additional expense.

`It is the object of the present invention to providea simple and effective method and apparatusl permitting `the direct recovery of ammonium sulphate from coal `distillation gases, and to avoid thereby the difculties experienced heretofore.

In carrying out the invention, the coal distillation gases derived, for example, from a coke oven, are subjected to suiicient cooling andpreferably to electrical precipitationv toeifect the separation of the heavy pitch constituents. Thereafter the gases are further cooled,` for example by radiation, so that the heavy oil ,is condensed. The gas is thus freed from heavy pitch l and oil constituents `and being at a relatively 10W temperature, the gas nis subjected in a primary condenser to contact with `a circulating body of ammonia liquor, With the` addition of `suicient Water to make up the `loss due `to evaporation in the condenser. A relatively concentrated am- "monia `liquor vis thus produced.` At the same time, carbolic oil is condensed and is separated from the ammonialiquor and Withdrawn.

' The gases are thenhconveyed to a reheater wherein ,their temperature is raised by indirect contact withtheheavy oil previously separated therefrom, and at this higher temperature the `gases are delivered to the saturator together with the strong ammonia liquor recovered'irorn -the condenserpand a regulated quantity of sulphuric acid. Inthe saturator ammonium Asulphate `is The heavy oil, after passing through the re` In Vthe recovery `of ammonium sulphate from nating current.

heater and being cooled therein, may be returned and utilized as an initial cooling agent for the gases leaving the coke ovens. The surplus of this heavy oil may be accumulated in any suitable receptacleand employed for purposes for Which it 30 is adapted. l

While the invention as described is adapted 'especially for the treatment of gases from coke of simple and relatively inexpensive apparatus, 0

is readily controlled, and is thus capable of producing ammonium sulphate in an economical :means of the heavy oil, Vand the temperature may be regulated so as to., cause the separation of the desired pitch constituents in the precipitator.

Y The operation of an electrical precipitator as commonly used consists in passing the gas to be treated between electrodes Whose difference kin `electrical potential is very great. Experience has shown that it is best to use a rectified alter- The alternating current (theV primary)` is sent through a step-.up transformer to produce the high potential current (the secondary) which is then rectified to an intermittent uni-directional current, for example by. means of a rotary converter. The rectified current is delivered from the converter to the electricalv precipitator at practically the potential at which it leaves the transformer. Y

The electrical precipitator consists commonly of a group of vertical pipes With a Wire or rod in the center of each, the pipes being connected to proper headers for the introduction and discharged of the gases. The `pipes generally constitute the positive electrodes, and the Wiresor rods the negative electrodes.` The size of the pipes may vary, but in general pipes of less than six inches in diameter are not used. Electrical precipitatois with. pipes six inches in diameter, using secondary voltages from 35,000 to 50,000 Volts, are satisfactory for the p .ipose of the invention. It is generally best to operate wi h maximum potential diierence (secondary cure rent) between the electrodes, this maximum bee ing just below the break-down voltage at which arcing occurs.

The eiciency of the cleaning is dependent upon several variables. Satisfactory cleaning of the gas may be accomplished if the time of treatment is of the order of one second, although `this time may be varied widely depending upon the character of the pitch to be recovered `from the gases passing through the precipitat 3. Yiorlc ing with tubes nine feet long and siX inches in diameter, with a gas velocity of from six to four and iive-teiiths feet per second, an efficiency oi cleaning oi approximately ninety-nine per cent can be obtained. in the practice of the inveiin tion the electrical precipitator may he operated at a suitable temperature to recover pitch oi the desired melting point. The ter perature of the gases leaving the electrical precipita-tor is preferably between about 209 and 350 C. l"Ehe pitch may be returned to the collector main recovered with the pitch produced therein by the cooling oi the frases trom their initial teni-- Aperatureof about '700o C.

cipitator. The terni pitch as used throughout the specification and in the claims is intended to refer to those constituents of coal distillation gases which are or may be separated by an electrical precipitator operated in accordance with the present invention and may include tai' and other condensable constituents or" the gases as well as thoseinaterials which are designated pitch in the strict sense of the term.

In passing from the electrical precipitator through the cross-over inain, the gases are cooled by radiation to a temperature o approximately 180D C., and the heavy oil still carried by the gases is thus condensed and may be withdrawn therefrom. In the continued passage of the gases through the foul gas main, a further reduction in the temperature to about 100o C; is accomplished by radiation, and at the latter temperature the gases are introduced to the primary condenser. At this point they gases, if we assume a coal moisture of five per cent, will have a dew point or" approximately 56 C. In the primary condenser the gasesv are subjected to direct contact with fixed ammonia liquor which maintained in circulation through the condenser with the water to make up the loss due to evaporation of about 22 pounds per ton of coal.' The gases are thus cooled to a wet bulb temperature o 6o C. The carbol-ic oil is condensed and withdrawn from the condenser separately from the circulatbeing to a pipe 28 which delivers the gases to a reheater ing ammonia liquor, a goed separation effected under the conditions specified. The carbolic oil is conveyed to a suitaole receptacle and may be utili-Zed for any desired purpose.

The gases leave the primary condenser and are delivered to the relie-atei", which is a heat exchanger, to which the heavy oil at about 18!D C. is conveyed. The gases arel thus roh-cated to a temperature of about 90 C., and at that teiiiperature are delivered to the sature/tor. The saturator is supplied with ammonia liquor from the primary condenser at-a concentration oi about addition of sufficient 150 to 200 grams per liter of ammonia and with sulphuric acid in the proportion required to combine with the ammonia. Ammonium sulphate is separated in the saturator and can be recovered therefrom.

From the saturator the gases are passed through an acid separator in which the acid is recovered and returned to the saturator, and they are delivered thence to a iinal cooler in which the gases are subjected to direct contact with water and their temperature reduced to about 25 C. At this temperature naphthalene is condensed and passesy with the water to a decanter inwhich naphthalene is recovered. The gases then pass through the benzol scrubber where henzol is separated, the gases being Aadaptedthen for use as fuel or otherwise. hereinbefore indicated, the cooling in the collector main may be effected by heavy oil, the latter being delivered from the reheater to a p mp which returns it to the collector main, so

eceptaele- The ,fention will be more clearly understood elererice t the accompanying drawing, which diagraininatically illustrates an apparatus suitahle for use in the practice of the invention, it bee well-known to those skilled in the art are gases and thus to separate heavy pitch constitruents therefrom. The gases are delivered by a pipe 9 to an electrical precipitator 10 of any suitvable form and construction wherein the gases are subjected at a suitable temperature to an clectricaldischarge for the purpose of removing further quantities of pitch constituents which are returned through a pipe 1l to the collector main. The pitch which accumulates in the collector rmain may be withdrawn through a pipe 12.

The gases freed from pitch constituents pass through the cross-over main 13, and the heavy oil which condenses therein is withdrawn through a pipe 14. The gases continue through a foul gas main 15 to the primary condenser 16 wherein they are subjected toconcentrated ammonia liqcondenser, is withdrawn through a pipe 22 and l is delivered to a receptacle 23.

The gases escape through a pipe 24 and pass through an exhauster 25, which maintains the pressures necessary for circulation of the gases 27. The latter is connected to the pipe 14, through which heavy oil isr withdrawn from the cross-over main. The heavy oil at relatively high temperature passes through the tubes of the reheater and thus heats the gases which are delivered thereto by the pipe 26. The heavy oil is recuculatedv by a pump 2,8 and is returned through a pipe 8 to the collector main. The surplus of the heavy oil is accumulated in a receptacle 29.

The reheated gases passthrough a pipe 30 to aV saturator 31 which is supplied with concentrated ammonia liquor through a pipe 31 `which is con-4 nected to the pipe `19. `Sulphuric acid is supplied through a pipe 30. `The ammonium'sulphate may be removed from the saturator to a receptacle 32, delivered thence to a centrifuge 33,

and conveyed to storage space by a conveyor 34.

The gases pass through a pipe 35Vto an acid separator 36, the acid being returned by a pipe 37 to the saturator. The gases then pass through a pipe 38to the final cooler 39 wherein they are subjected to direct contact with water supplied through a pipe 40. The water, which carries naphthalene separated in the condenser, is delivered by pipe 41 to a decanter 42 in which the naphthalene is recovered, VThewater may be discharged.

The cooled gases are delivered through a pipe 43 to benzol scrubbers 44 and 45 which are connected by a pipe 46. The gases may be delivered through a pipe 47 to a gasometer or other receptacle (not shown). i

The condensers, reheater, saturator, and scrubbers' are each standard forms of apparatus well 4known in the art. Similarly theelectrical precipitator employed may be the well known formV of precipitator which has been utilized hereto-` for in the separation of tar and pitch constituents from distillation gases.V No further and more detailed description of the apparatus is` necessary, anyrof the usual forms of such apparatus being adapted for utilization in the practice of the method.

Various changes may be made in the details of construction and arrangement, therefore, and in the procedure as described, without departing from the invention or sacricing any of the advantages thereof.

I claim: v1. The process for the recovery of free and fixed ammonia from coal distillation gases which comprises (l) washing the hot gases with heavy oil to remove pitch and heavy oil therefrom; (2) thereafter recirculating aqueous liquor in contact with the pitch and heavy oil-free gas to remove fixed ammonia therefrom; (3) passing the fixed ammonia-, pitchand heavy oil-free gas through sulphuric acid; and (4) withdrawing excess aqueous liquor containing fixed ammonia from step (2) and. introducing it into the sulphuric acid employed in step (3).

2. The process for the recovery of free and fixed ammonia from coal distillation gases which comprises (1) washing the hot gases with heavy ico acid; and (6) withdrawing excess aqueous liquor v Y from step (3) and introducing it into the sulphuric acid employed in step (5) WILLIAM B. WINGERT. 

